Over the years there have been many attempts to construct a sole unit for an athletic shoe to meet varying requirements of feel, function and support as well as to construct the sole unit of varying materials. To this end, there have been attempts to provide a sole unit for better memory and dispersion of shock during running, as well as to meet other demands of various running groups.
One suggestion for improving a sole unit described by the prior art relates to the encapsulation by polyurethane of a medium, such as a bag filled with an inert gas, for example, nitrogen. Thus, it was the intention of the prior art to provide a sole unit which would retain certain desired characteristics imparted by the polyurethane material comprising the shell surrounding the air bag, and, at the same time, to impart from the core of the sole unit other characteristics not obtained by a midsole formed entirely of polyurethane.
While an athletic shoe of the described type may provide many desired and sought-after results, the athletic shoe of the present invention is considered to be an improvement over the known prior art.